3 - BLOODSTAIN PATTERN ANALYSIS (BPA)

Bloodstain pattern analysis (BPA)

is the examination of the shapes, locations, and distribution patterns of bloodstains,

• in order to provide an interpretation of the physical events which gave rise to their origin

• Passive

• Transfer

• Active (Projected)

TYPES OF BLOOD STAINS:

Passive Stains

These are drops created by the force of gravity acting alone.

• Examples are drops, flows and pools.

Transfer Stains

This results from objects encountering existing bloodstains and leaving wipes, swipes or pattern transfers behind.

• Examples include a bloody shoe print, handprint or a bloody body dragged against the floor.

Active (Projected) Bloodstains

result from blood projecting through the air and are usually seen as spatter

• For example, gushes, splashes and arterial spurts.

Rule of Thumb

As the impact angle goes down, bloodstain shape becomes more elongated. 

Gunshot spatter

includes both forward spatter from the exit wound

and back spatter from the entrance wound.

Cast-off

results when an object swung in an arc or a geometric curve flings blood onto nearby surfaces.

• This occurs when an assailant swings the bloodstained object back before inflicting another blow.

Arterial spray

Arterial patterns result from blood projected into the scene under pressure from the artery or heart.

Expirated spatter

is usually caused by blood from an internal injury mixing with air from the lungs being expelled through the nose, mouth

• or an injury to the airways or lungs.

• Low

• Medium

• High

BLOOD STAINS CAN ALSO BE CLASSIFIED ACCORDING TO VELOCITY:

Low

Blood drops into blood and footstep spatters 

Medium

blood flicked off finger and blunt object used on victim 

High

gunshots and propellers 

• liquid (plasma and serum)

• solids (red blood cells, white blood cells, platelets, and proteins)

Blood contains both:

liquid state

Blood is in a _____ when inside the body. 

clots

• prolonged

When it exits the body, it starts to coagulate to form ___:

• Hence, the presence of blood clots in bloodstains can indicate that the attack was _____,

• or that the victim was bleeding for some time after the injury occurred. 

• 8%

• males

• females

• On average, accounts for  ___ of total body weight 

• 5 to 6 liters of blood for ____. 

• 4 to 5 liters of blood for _____

Parent Drop

A drop of blood from which a cast-off or satellite spatter originates. 

Satellite Spatter

Small droplets that break off from the parent spatter upon impact with a target surface. 

• Pattern Analysis

• Reconstruction

BPA 2 PHASES:

Pattern Analysis

looks at the physical characteristics of the stain patterns

• including size, shape, distribution, overall appearance, location and surface texture where the stains are found.

• Analysts interpret what pattern types are present and what mechanisms may have caused them.

Reconstruction

uses the analysis data to put contextual explanations to the stain patterns:

• What type of crime has occurred? Where is the person bleeding from? Did the stain patterns come from the victim or someone else? Are there other scene factors (e.g. emergency medical intervention, first responder activities) that affected the stain patterns?

Luminol

is a chemical agent that exhibits luminescence in form of a blue glow

• when mixed with an appropriate oxidizing agent. 

Hemoglobin

in blood contains iron(Fe) which is the oxidizing agent.

• It reacts with Iron in the blood to produce luminescence. 

Void Patterns

A void occurs when a person or object blocks the path of the blood.

Forensic Toxicology 

the use of detecting and identifying the presence of drugs and poisons

• in body fluids, tissues, and organs to aid medical or legal investigation. 

hemlock

Earliest recorded use of poison was Socrates’ execution

• in 339 BC via ingestion of _____

Paracelsus

observed that any substance could be a poison, depending on its dose: 

• "All things are poison and nothing is without poison; only the dose makes a thing not a poison." 

Orfila

was the first to articulate the fact that poisons must be absorbed, or enter the blood, to manifest their effects. 

• Microbicide

• Herbicide

• Pesticide

Types of Poisons:

Microbicide

used to reduce infectivity of microorganisms 

• EXAMPLE: chlorine, peroxide, antibiotics 

Herbicide

used to kill unwanted plants

• EXAMPLE 2,4-D, atrazine, glyphosate (Roundup) 

Pesticide

used to kill unwanted animals

• EXAMPLE DDT, pyrethrin, nicotine 

• Hemotoxin

• Necrotoxin

• Neurotoxin

Types of Toxins:

Hemotoxin

destroy red blood cells

(EX: pit vipers) 

Necrotoxin

cause cell & tissue death

(EX: brown recluse spider, “flesh-eating bacteria”) 

Neurotoxin

affect the nervous system

(EX: Black widow spider, scorpions) 

• Fang-released ( EX:snakes, centipedes, spiders) 

• Sting-released (EX:bees/wasps/ants, scorpions) 

• Other methods ( EX: Hairs (caterpillars), Tentacles (jellyfish), Saliva (Gila monster), Fins (lionfish, stingrays) ) 

Types of Venoms:

Toxicity

The degree to which a substance (a toxin or poison) can harm humans or animals. 

Acute toxicity

involves harmful effects in an organism through a single or short-term exposure. 

Subchronic toxicity

the ability of a toxic substance to cause effects for more than one year but less than the lifetime

of the exposed organism.  

Chronic toxicity

is the ability of a substance or mixture of substances to cause harmful effects over an extended period, usually upon repeated or continuous exposure, sometimes lasting for the entire life of the exposed organism

Dosage

the most important and critical factor in determining if a substance

is an acute or a chronic toxicant.

LD50

refers to amount of substance that would kill 50% of test population within 4 hrs. 

Toxicologist

• Must identify one of thousands of drugs and poisons 

• Must find nanogram to microgram quantities dissipated throughout the entire bod

• Marquis Test

• Scott Test

• Duquenois-Levine

Presumptive/Screening: (3)

Marquis Test

Turns purple = opiates  

Turns orange brown = amphetamines 

Scott Test

Turns blue

= cocaine 

Duquenois-Levine

Turns purple

= tetrahydro-cannabinal 

• Microcrystalline Tests

• Chromatography

• Mass Spectrometry

• IR Spectroscopy

 

Confirmatory Tests:

Microcrystalline Tests

Identifies drug by using chemicals that react to produce characteristic crystals  

Chromatography

Separates drugs and gives tentative ID

Mass Spectrometry

Chemical “fingerprint” – no two drugs fragment the same 

IR Spectroscopy

IR light is absorbed by different chemicals